全新java初学者实践教程6(Java SE5.0版)
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基本语法3
J HV ?_v_*+b_ ;7QG]JX 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
rFUd t2|0no [font="Times] 1.循环语句[font="Times]:while,do-while,for
/gex0w O7yj< [font="Times]2.分支语句[font="Times]:if-else,switch,
r=p^~tuyxr [font="Times]
AJ3Byb=. 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
cIK4sOTJ& [font="Times]
_1WA:7$C 4.异常处理语句[font="Times]:try-catch-finally,throw
.Yz^r?3t +ZFN8 实践:
M&sQnPFH [font="Times] 1.循环语句
NLUO{'uUW [font="Times] while 语句
t**d{P+ [font="Times]class While {
m9]Ge] [font="Times]public static void main(String args[]) {
Rm6i[y& [font="Times]int n = 10;
oZdY0n h4 [font="Times]while(n > 0) {
(E~6fb"c [font="Times]System.out.println("tick " + n);
ZS`Kj(D [font="Times]n--;
8o.|P8% [font="Times]}
=H}x [font="Times]}
c>Ri6=C [font="Times]}
D 5:'2i [font="Times] do…while 语句
Fq%NY8KNE [font="Times] class DoWhile {
+8"P*z, [font="Times]public static void main(String args[]) {
bQPO'S4 [font="Times]int n = 10;
(m=1yj9 [font="Times]do {
E b CK9 [font="Times]System.out.println("tick " + n);
A"R(?rQi= [font="Times]n--;
g1]bI$; [font="Times]} while(n > 0);
P\QbMj1U [font="Times]}
%;<g!Vw.k [font="Times]}
L|;sB=$'{ 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
ZF8`=D`:R [font="Times] for语句
FPPl^ [font="Times] class ForTick {
rEbH<| [font="Times]public static void main(String args[]) {
NgF"1E [font="Times]int n;
oiD{Z [font="Times]for(n=10; n>0; n--)
ml!c0< [font="Times]System.out.println("tick " + n);
)h{+pK [font="Times]}
x|()f3{. [font="Times]}
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与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
#.C2_MN> 还有啊,[font="Times]for循环的部分可以为空的
)5y"T0] [font="Times]class ForVar {
<Q`3;ca^ [font="Times]public static void main(String args[]) {
0O-"tP8o [font="Times]int i;
( )f) [font="Times]boolean done = false;
xD sKb_ [font="Times]i = 0;
;>F1?5P{ [font="Times]for( ; !done; ) {
Y0m?ZVt [font="Times]System.out.println("i is " + i);
yJ6g{#X4K< [font="Times]if(i == 10) done = true;
q|r*4={^!* [font="Times]i++;
e@/' o/ [font="Times]}
SMfa(+V I [font="Times]}
A5]yC\*zt [font="Times]}
循环语句的例子下载 e<FMeg7n [font="Times] 2.分支语句[font="Times]
Z`zLrXPD) [font="Times] if/else语句
4X+I2CD [font="Times]class IfElse {
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l
[' [font="Times]public static void main(String args[]) {
<'7s3 [font="Times]int month = 4; // April
x"cB8bZ!$ [font="Times]String season;
IYH4@v/# [font="Times]if(month == 12 || month == 1 || month == 2)
5g$>J)Ry [font="Times]season = "Winter";
mAJ'>^`^ [font="Times]else if(month == 3 || month == 4 || month == 5)
Kb1@ + [font="Times]season = "Spring";
r:4]:NKCi [font="Times]else if(month == 6 || month == 7 || month == 8)
YD{N)v [font="Times]season = "Summer";
?{5}3abB` [font="Times]else if(month == 9 || month == 10 || month == 11)
X|QokAR{$> [font="Times]season = "Autumn";
.])X.7@x [font="Times]else
:VLYF$| [font="Times]season = "Bogus Month";
Q/*|ADoq [font="Times]System.out.println("April is in the " + season + ".");
A..`?oGj [font="Times]}
=^_a2_BBl [font="Times]}
G2+ gEg [font="Times]//这段程序输出[font="Times]:
$M+'jjnP [font="Times]//April is in the Spring.
u`Y~r<?P( [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
d\tY-X3 [font="Times] switch语句
FV,aQ# [font="Times] class Switch {
Dca,IaT' [font="Times]public static void main(String args[]) {
H0.A;` [font="Times]int month = 4;
-})zRL0!' [font="Times]String season;
Z+[W@5q [font="Times]switch (month) {
f/4DFs{ [font="Times]case 12:
iun_z$I<+Z [font="Times]case 1:
.j=mT[N,I [font="Times]case 2:
'op_GW [font="Times]season = "Winter";
]<c\+9 [font="Times]break;
^62I 5k/u [font="Times]case 3:
<U\8&Uv> [font="Times]case 4:
NA`8 ^PZ [font="Times]case 5:
g-NrxyTBlx [font="Times]season = "Spring";
-w5sXnS [font="Times]break;
Iek]/= [font="Times]case 6:
%T\2.vl [font="Times]case 7:
J8Vzf$t}; [font="Times]case 8:
Gi2Fjq/Y [font="Times]season = "Summer";
*Tr{a_{~C [font="Times]break;
8F's9c, [font="Times]case 9:
OjqT5<U [font="Times]case 10:
EQ|Wke [font="Times]case 11:
L.}sN. [font="Times]season = "Autumn";
Kxz|0l [font="Times]break;
~ tN/ [font="Times]default:
BglbQ'6p [font="Times]season = "Bogus Month";
UISsiiG( [font="Times]}
D";clP05K [font="Times]System.out.println("April is in the " + season + ".");
sBqOcy [font="Times]}
VwK7\jV [font="Times]}
分支语句代码下载 Ai5+ ;8z+
K\s<<dRa [font="Times]switch语句适合于条件非常多的逻辑
-dfs8 [i 请看上述语句可以混合使用,请看
下载例子